ATS Red Light Camera Claims Driver Pulled 4g Turn

The city of St Petersburg, Florida uses camera systems sold by American Traffic Solutions (ATS, formerly American Traffic Systems) to issue tickets to drivers allegedly running red lights. According to The Newspaper, when the activists at St Petersburg Red Light Cameras reviewed logs of the 21,602 photo tickets issued in the city from October 29, 2011 to April 30, 2012 they discovered that the ATS cameras were reporting that they “measured” Bugatti Veyron level speeds from cars not realistically capable of that kind of velocity.

Florida law prohibits automated speeding tickets, but the ATS cameras used to enforce red-lights still record motorists’ alleged speed. Red light cameras all measure vehicle speed in order to turn on the camera at the correct time. While nobody was cited for speeding due to the aforementioned Florida statute, the fact that ATS’ technology cited literally unbelievable speeds might call into question just how reliable their systems in general are. If they get speed wrong, what else don’t they get accurately? ATS claims that their cameras don’t lie, but the speeds cited are not just incredible but also not credible. At one intersection, a woman was measured as going 157 MPH as she went past the camera. At another, a lady was said to have been gong 170 MPH. While those speeds are unusual, there are indeed a small number of road cars that can see the other side of 150. However, to my knowledge there is only a tiny number cars capable of 210+ MPH, and the car that ATS recorded as going 215 MPH at 66th St and 38th Ave was not made by Bugatti, Lamborghini or a similar exotic car manufacturer.

Those were straight line speeds and, as I mentioned, there are cars on the road capable of those speeds, when going straight. The ATS cameras, though, also recorded cornering speeds that are simply not possible, at least outside of a race track and even then they’re so extreme as to not be believable.

On April 12, 2012, a man was accused of making a right-hand turn at 96 MPH at the corner of 34th Street and 22nd Avenue. Now I don’t race competitively but TTAC has our resources so I asked Jack Baruth if that was physically possible. JB kindly sent me a chart that indicated G forces at particular speeds based on the radius of the turn. I printed out Google’s satellite view of that intersection and measured the turn radii at the two corners under surveillance. Based on the location of the two cameras, the driver had to be traveling on 34th, turning onto 22nd, though the cited speed was not likely achieved on any of that intersections 4 corners.

From a print out of the satellite shot I determined that one corner has about an 80′ radius for the right turn lane. The other corner is a tighter turn, actually a sharp turn in, then a constant radius. I figure the effective radius is closer to 50′ in that turning lane. In either case, 96 mph would be off the chart, literally. Jack’s cornering speed charts don’t go below a 100′ radius. Even bumping up the radius to 150′ maxes out at 94.5 MPH and 4.0 Gs! To give you some perspective, for a road car, anything over 0.9 G is considered to be very good cornering. A small number of the very best handling production cars might slightly exceed 1 G on a skid pad, under steady state conditions. At 4 Gs in a road car, I’d be worried about parts breaking off. Can a road tire withstand 4 Gs without separating from the rim or some other failure?

Now on a race course drivers don’t have to abide by things like right turn lanes. They use as much of the road surface as they can, usually going wide on approach and turn in, hitting the apex tight, and then going wide on exit. What that does is create the widest possible radius on the turn, maximizing cornering speed. Even if the cited driver was genuinely “driving in a racelike manner”, using the entire road, driving in the wrong direction on entry and exit, the radius works out to only be about 200 feet. At 96 MPH, on a 200 feet radius turn, the driver would still have been pulling over 3.0 G.

Maximum loading under cornering in a Formula 1 car on a race track is generally quoted in the 3.0-4.5 G range. ATS cameras say that drivers in St Petersburg are seeing cornering speeds with that level of lateral acceleration. Either people are getting ticketed by a system with proven unreliability (at least in terms of measuring speed), or American Traffic Solutions thinks that there are a lot of budding F1 drivers in the St Petersburg area.

Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can dig deeper at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS